Acoustic Positioning and Navigation System for GNSS Denied/Challenged Environments

Current navigation sensors mostly rely on electromagnetic signals for getting the position, velocity, and time (PVT) information. But it can be observed that mammals like bats use acoustic waves, mostly ultrasound, for echolocation. Acoustic waves are also used by cetaceans like dolphins and sperm whales for echolocation. This paper investigates the performance of the acoustic positioning and navigation system (APNS). Acoustic sensors have relatively lower cost, size, weight, and power (C-SWAP) and are easy to deploy. Additionally, being based on acoustic signals, this technique is immune to signal-in-space electromagnetic interferences. The attenuation of sound in air is discussed along with potential ranging errors and signal delays. A multistatic arrangement of sensors is discussed in detail, with an optimized arrangement of transmitters in a given test geometry. The transmitters broadcast their respective signals following a Time Division Multiple Access (TDMA) scheme. The receiver position is calculated based on ranging measurements from a minimum of three transmitters. The range is calculated based on the Time of Arrival (TOA) of acoustic waves from the transmitter to the receiver. The transmitters are arranged optimally to minimize Position Dilution of Precision (PDOP) as well as maximizing sensor availability. The error in positioning due to platform dynamics is also discussed. This analysis lead to an optimized arrangement of transmitters, thus supporting subsequent experimental activities.